Question

Without adding find the sum of first 10 odd natural numbers

Answer 1

Answer:

The first 10 odd numbers are

1, 3, 5, 7, 9, 11, 13, 15, 17,19

The standard mathematical method of getting the sum of a series would be to add the first number of the series to the last number of the series and multiply the sum by one half the number in the series.

1 + 19 = 20

20 × 5 = 100 ( there are 10 odd numbers in the series, so half of them would be 5.

Thus the sum is 100

Explanation:

Answer 2

The n-th odd number is 2n+1. If the sum of the n first odd numbers is n^2, then the sum of the first (n+1) odd numbers is n^2+2n+1 = (n+1)^2. Therefore, the sum of the first 10 odd numbers is 10^2 = 100.

Hopefully this helps you